Binary Multi-Leaf Collimator Drive for Real-Time Tumor Tracking
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Solution Overview
Problem
Existing radiation therapy systems struggle to accurately irradiate tumor tissue in real-time due to changes in tumor geometry and patient anatomy, leading to potential exposure of non-tumorous tissue during treatment sessions.
Innovation Solution
A high-bandwidth multi-leaf collimator system with rapid leaf movement mechanisms, such as cam-based, spring-based, fluid-power, and electromagnetic systems, capable of transitioning leaves between open and closed states in less than 10 milliseconds, allowing for precise radiation delivery based on real-time tumor data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional multi-leaf collimators are used with standard leaf movement mechanisms, then the system structure is simpler and more reliable, but the leaf transition time is too long (greater than 10 ms) to achieve real-time radiation delivery based on detected tumor emissions
Solution Approach 1:
The collimator is divided into multiple independently controllable leaves, each capable of moving between open and closed positions. This segmentation allows selective radiation blocking of specific beamlets while maintaining overall system functionality, enabling real-time adaptation to tumor position changes without requiring complete system redesign.
Solution Approach 2:
The collimator transitions from a static configuration to a dynamic system where leaves can rapidly move between positions. The drive mechanisms (cam-based, spring-based, fluid-power, or electromagnetic) enable leaves to transition in less than 10 ms, allowing the system to adapt to real-time tumor position changes detected by emission imaging.
2Adaptability or versatility
If treatment plans are devised in advance based on tumor images, then the treatment plan can be thoroughly designed and optimized, but the plan cannot account for changes in tumor geometry and patient anatomy during the treatment session
Solution Approach 1:
The system performs preliminary detection of tumor emissions using gamma cameras or PET detectors to determine tumor position before radiation delivery. This preliminary action allows the control system to pre-calculate the appropriate leaf positions needed to target the tumor, minimizing the time delay between detection and treatment.
Solution Approach 2:
The system implements a feedback loop where tumor emissions are continuously detected, leaf positions are adjusted based on detected tumor position, and radiation is delivered in real-time. This closed-loop control enables the system to adapt to tumor position changes during treatment, maintaining precision without significant latency.
3Object-affected harmful factors
If the collimator leaves are made with high-Z materials throughout the entire leaf structure, then the radiation shielding effectiveness is maximized, but the leaf weight increases making rapid movement difficult
Solution Approach 1:
High-Z materials are applied selectively only to the portions of the leaves that require radiation shielding (the radiation-attenuating portions), while other portions use lighter materials. This local application of high-Z materials maintains adequate radiation protection while significantly reducing overall leaf weight, enabling faster acceleration and positioning.
Solution Approach 2:
The leaves are constructed as composite structures combining high-Z radiation-attenuating materials with lighter structural materials. This composite approach provides the necessary radiation shielding effectiveness while keeping the overall leaf mass low enough to achieve the required transition speeds of less than 10 ms.
4Loss of time
If the collimator is designed for high-speed operation with reduced leaf weight, then the leaf transition time is reduced to enable real-time tracking, but the radiation shielding capability may be compromised
Solution Approach 1:
The leaf design concentrates high-Z shielding materials only in the regions that require radiation attenuation, rather than uniformly distributing them throughout the entire leaf structure. This localized shielding approach maintains adequate protection capability while minimizing overall leaf mass, enabling transition times of less than 10 ms.
Solution Approach 2:
The leaves utilize composite construction with high-Z materials strategically positioned to provide radiation shielding where needed, combined with lighter structural materials for the remaining portions. This composite design achieves the necessary balance between shielding capability and rapid movement performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables precise and timely radiation application to tumor sites, reducing exposure to healthy tissue and shortening treatment sessions by compensating for tumor and patient movements.
Implementation Method 1
a spring system coupled to the leaf shaft and configured to apply forces along a longitudinal axis of the leaf shaft
Implementation Method 2
an actuator system coupled to the leaf shaft... The actuator system may comprise a first configuration where the leaf is retained in the first location and a second configuration where the leaf is retained in the second location
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
Described herein are multi-leaf collimators that comprise leaf drive mechanisms. The leaf drive mechanisms can be used in binary multi-leaf collimators used in emission-guided radiation therapy. One variation of a multi-leaf collimator comprises a pneumatics-based leaf drive mechanism. Another variation of a multi-leaf collimator comprises a spring-based leaf drive mechanism having a spring resonator.